As used herein clutch means a device for coupling two working parts such as the engine and driveshaft of an automobile. In automobiles, manual clutches make use of friction to transmit rotation of the engine crankshaft to the gearbox, and then to the wheels. Moreover, manual clutches use friction linings on a clutch plate to allow the plate to slide before it becomes fully engaged, so that the rotation can be taken up slowly in order to make the automobile move smoothly. Specifically, in a car with a manual gearbox, the clutch is disengaged by pressing down on a clutch pedal to raise a pressure plate away from the clutch plate, disconnecting the flywheel and crankshaft from the transmission shaft. When the clutch pedal is lifted, springs force the pressure plate and clutch plate against the flywheel.
As used herein, synchronized shifting means a gear system by which driving and driven members are brought to the same speed before engaging. Synchronized shifting is accomplished by a collar sliding along the transmission shaft and rotating with the transmission shaft. The collar fits over a cone on the gear wheel, making the wheel speed up or slow down until both are moving at the same speed. The outer toothed ring on the collar then engages the teeth on the cone, locking the collar to the gear wheel.
As used herein, "transmission" means a device that transmits power from the engine of an automobile to the driving wheels and varies the speed ratios between them. As used herein, automatic transmission means a transmission in which the speed ratios are automatically selected and engaged. Automatic transmissions contain a torque converter and an automatic gearbox. The torque converter passes power from the engine flywheel to the gearbox progressively and smoothly. The automatic gearbox contains two sets of epicyclic gears in which gear wheels rotate at different speeds. Except in top gear, the speed of the flywheel is reduced so that the car wheels turn more slowly but with more torque. Reverse gear reverses the direction of the transmission output shaft and therefore the direction of the wheels.
Major automakers have disclosed development of a "stepless automatic" transmission based on British Technologies Group licensed "Torotrak" technolgy for development of an infinitely variable transmission (IVT). The Ford development is based on a "variator" comprising two clusters of free-wheeling rollers hydraulically clamped between two pairs of opposed toroidal discs where the outer discs of each pair are turned continuously by the engine and the rollers take the drive to the two inner, output discs. Tilting the rollers changes the ratio changing the working diameters of the input and output discs. The variator is combined with a single three-element planetary gearset providing a unique "geared neutral" for starting from rest, thereby replacing the usual torque converter. At a critical disc ratio, the two input elements rotate in opposite directions and the third output element is stationary providing no drive to the wheels. By changing the disk angles, the drive is engaged in either forward or reverse. U.S. Pat. No. 5,961,418 discloses an infinitely variable transmission. U.S. Pat. No. 5,295,920 discloses an automatic transmission having a belt type infinitely variable gear housed in a transmission casing. U.S. Pat. No. 4,885,955 discloses a multimode infinitely variable traction roller transmission including a toroidal traction roller transmission for infinitely varying the transmission ratio in each of the modes. U.S. Pat. No. 4,635,494 discloses an infinitely variable transmission with a lever or walking beam having variable fulcrum point. U.S. Pat. No. 4,526,060 discloses a compound planetary gear set used to provide an idle speed control and a vehicle speed control on an automotive type carburetor valve. U.S. Pat. No. 3,429,201 discloses a shaft that is offset from the wormgear or wormwheel with the worm speed controlled by a motor. The speed controls are rotational to the speed of the output shaft. U.S. Pat. No. 3,146,636 discloses a wormgear that is driven with a shaft that has a planet gear and meshes with the pinion.
What is needed beyond the prior art is a simple infinitely variable transmission that has the advantage of a frictionless clutch and the advantages of a stepless transmission.